This invention relates generally to signal propagation systems and, more particularly, to such systems in which a signal in the form of radiation, such as electromagnetic radiation, is propagated through a medium or through space, usually between a transmitter and a receiver. It should not be inferred, however, that the invention pertains only to communication systems. As will become apparent from this specification, the invention also has application to other signal propagation systems, such as the use of electromagnetic or particle radiation in the analysis of specimen structure.
In many situations in which an electromagnetic radiation signal is transmitted through a medium (including a vacuum), a relatively high level of energy is used to transmit the radiation signal. Moreover, it is almost uniformly accepted that high energy levels are needed for propagation of the radiation signal. Yet there are many applications in which it would be advantageous to reduce the transmitted energy level. Prior to the present invention, no one has been able suggest how this goal might be accomplished.
A notable example of an application appropriate to the invention is the transmission of data such as text, video, or audio, using electromagnetic radiation. With the prodigious volume of such information now being transmitted over ground-based transmitters and receivers and over satellite links, a substantial reduction in energy usage would be highly desirable. This reduction would be particularly advantageous when applied to a transmitter at a remote site, such as on a satellite, for which electrical power is severely limited. In other situations, it would be equally advantageous to provide a substantially increased signal range for a given power consumption.
Another class of applications relevant to this invention concerns the use of electromagnetic or particle radiation in the analysis of specimen structure. Such applications known in the art are inclusive of virtually the entire electromagnetic spectrum from radio waves through x-rays and of a wide variety of specimens. A specific example is the inspection of manufactured semiconductor structure. It would be desirable to accomplish this task with x-ray inspection beams having an ultra-low energy content instead of the relatively high energy content that must presently be employed.
In one class of radiography applications, the specimen to be analyzed is subject to damage from energy deposited by an incident radiation beam. A goal that has eluded researchers in this area is to make use of physical properties of a specimen, such as refraction, reflection, or phase shifting, to analyze the specimen without concurrent energy deposition. The ultimate goal in specimen analysis is three-dimensional reconstruction of a specimen image without the use of energy in the incident beam.
It will be appreciated from the foregoing that there are variety of applications using radiation signal propagation for which it would be highly desirable to employ radiation of significantly reduced energy content, without commensurately reducing the detectability of information carried on the signal being propagated. The present invention, as will now be described, accomplishes this goal in an elegant, completely novel and, perhaps, revolutionary manner.